Eris

The body that demoted Pluto

Only spacecraft can see it

Eris, a small icy world very far away, with the Sun shrunk to a star among the stars.

The numbers

Diameter: 1,445mi(2,326 km)A little less than Pluto
How much it weighs: 27percent more than Pluto
Distance from the Sun: 9,070,000,000mi(14,600,000,000 km)3,500,000,000 to 9,070,000,000 mi (5,600,000,000 to 14,600,000,000 km)
What it is: An icy body beyond Neptune
When it was classified: August 24, 2006, as a dwarf planet

To get an idea

At the farthest point of its orbit it reaches about twice Pluto's greatest distance.

From its farthest point the Sun looks only like the brightest of the stars.

Fun facts

These are not in the book: there was no room on paper.

At its farthest point it reaches about twice the greatest distance Pluto ever gets to.
It belongs to the scattered disk, a region even farther out than the Kuiper Belt.
Its name comes from the Greek goddess of strife, and it could not be more fitting.
No space probe has ever come near it, and none is on its way there.
It has a moon, and its name recalls the daughter of the goddess of strife.

Test yourself

The first question is the one printed under the QR code, with the answer the book did not give. The other four only exist here.

Question 1 of 5★ is the one from your book

Why is Eris important?

Question 2 of 5

Is Eris bigger or smaller than Pluto?

Question 3 of 5

Why does it weigh more even though it is smaller?

Question 4 of 5

What is the orbit of Eris like?

Question 5 of 5

Has any probe visited Eris?

Riddles

I carry the name of a goddess who stirs up quarrels, and I earned it: my discovery forced astronomers to redo the definitions and take a title away from someone else. What am I?

I am a tiny bit smaller than a famous neighbor of mine, and yet I weigh more: it means that inside I have more stone and less ice than it does. What am I?

I live so far away that from here the central fire is only the brightest of the stars. No human machine has ever paid me a visit. What am I?

Try it yourself

Activity 1

On a six-foot string, mark the Sun at one end, the Earth one inch away and Pluto at forty inches: at its farthest, Eris would go past the end of the string.

Activity 2

Draw a very squashed ellipse with the Sun off to one side: that is the shape of the orbit of Eris, not a circle.

The words

eccentric orbit: A very stretched orbit, in which the distance changes a lot.

Sources: Wikidata (Q3989), Wikipedia (Eris (astronomia)).